1. Field of the Invention
The present invention relates to an image erasing device having a cleaner for erasing an image displayed on a display medium. The present invention also relates to an image display apparatus equipped with the image erasing device, and an image-recording apparatus equipped with the image erasing device, and an ink.
2. Related Background Art
Known image-display apparatuses include apparatuses employing a magnestyrus display medium or a liquid crystal display medium, and electric blackboards and whiteboards. These image-display apparatuses use a display medium repeatedly by erasing the displayed image to form another image. However, the method employing a magnestyrus, which uses repeatedly a monochromatic magnetic material, is difficult to be used for a color display. The method utilizing a liquid crystal has disadvantages such as low contrast of the displayed image, a small view angle, necessity for a backlight, relatively large power consumption for retaining the display due to the lack of memorizability, and so forth. Generally a physical method or a chemical method is employed for erasing an image recorded by an uncostly recording with a felt-pen or an ink-jet printer without the above disadvantages.
Image display apparatuses equipped with a physical erasing means are disclosed in Japanese Patent Application Laid-Open Nos. 5-160940, 6-64390, and 8-156491. In the disclosed apparatuses, an erasing pad having a length equal to the width of the display medium is brought into contact with the recording medium, and the erasing pad is relatively moved in the direction of feeding the display medium to erase a displayed image. A display apparatus equipped with an erasing means moveable independently of a display medium is disclosed in Japanese Patent Application Laid-Open No. 10-250287.
Image display apparatuses equipped with a chemical erasing means are disclosed in Japanese Patent Application Laid-Open Nos. 8-100140 and 8-106261. The disclosed apparatuses employ a liquid-absorbing means such as paper and a water-soluble polymer as the image display medium and are equipped with a means for erasing the image by use of a water-soluble erasing liquid. An apparatus equipped with an image erasing means employing light irradiation is disclosed in Japanese Patent Application Laid-Open No. 5-16342.
After comprehensive investigation, the inventors of the present invention noticed that, in the methods of the above-cited Japanese Patent Application Laid-Open Nos. 5-160940, 6-64390 and 8-156491, the erasing performance deteriorates by repeated use owing to accumulation of print dregs in the erasing pad, or turn-up or tailing of the erasing pad, and that the erasure can be imperfect owing to a large width of the cleaner causing nonuniform pressure-contact with the display medium, disadvantageously. The aforementioned Japanese Patent Application Laid-Open No. 10-250287 discloses neither a feeding means for feeding the display medium, nor erasure of the printed image during feeding of the display medium.
The methods of erasure with an erasing liquid disclosed in Japanese Patent Application Laid-Open Nos. 8-100140 and 8-106261 cause problems in replenishment of the erasing liquid and disposal of the waste liquid after the erasure. In the light irradiation method disclosed in Japanese Patent Application Laid-Open No. 5-16342 to render the ink invisible, the ink layers are superposed successively, so that the service life of the display medium is disadvantageously short.
The inventors of the present invention comprehensively investigated on effective and reliable methods for erasing an image on a display medium of an image display apparatus having a feeding means for feeding a display medium. As the results, the inventors of the present invention found that the image on the display medium can be reliably erased by feeding the display medium stepwise intermittently and driving a cleaner to scan the display medium in the direction perpendicular to the feeding of the display medium while the display medium stays stationary. Thus the present invention has been completed.
An object of the present invention is to provide an image erasing device, comprising a feeding means for feeding a display medium or a recording medium, and an erasing means for reliably erasing an image formed erasably on a recording medium, and an ink.
Another object of the present invention is to provide an image display apparatus equipped with the image erasing means.
A further object of the present invention is to provide an image recording apparatus equipped with the image erasing means.
The image erasing device embodying the present invention for erasing an image formed erasably on a recording medium comprises a means for feeding the recording medium stepwise, and a cleaner for erasing the image formed on the cleaner by independently scanning the recording medium perpendicularly to the direction of feeding of the recording medium while the recording medium stays stationary.
The image display apparatus, embodying the present invention, equipped with an image erasing means comprises a display medium, a means for feeding the display medium stepwise, and a cleaner for erasing the image formed on the display medium by independently scanning the cleaner perpendicularly to the direction of feeding of the display medium while the display medium stays stationary.
The image recording apparatus, embodying the present invention, equipped with an image erasing means comprises a means for feeding a recording medium stepwise, a cleaner for erasing the image formed on the recording medium by independently scanning the cleaner perpendicularly to the direction of feeding of the recording medium while the recording medium stays stationary, and an image-forming means for forming an image erasably on the recording medium.
The ink, embodying the present invention, comprises a pigment of one color selected from yellow, magenta, cyan, and black at a content ranging from 1% to 10% by weight, a polymer emulsion at a content ranging from 0.001% to 0.5% by weight, a glycol at a content ranging from 0% to 10% by weight, and an alcohol at a content ranging from 0% to 20% by weight based on the total weight of the ink.